orthopaedic plaster cast related content
Wednesday 5th April 2017
The patient’s history was of a severe motorcycle injury two days previously. The patient was admitted to hospital and the request for a full below knee cast to be applied was made to the plaster room staff. The injury was a very obvious bi-malleolar fracture with a significant degree of talar shift. The lateral radiograph had demonstrated that there was also a posterior malleolus fracture.
The patient was supposed to be discharged from hospital that very day and he was to be managed at home until the next outpatient fracture clinic which was for some ten days hence. I have no idea how this patient’s injuries had managed to escape being discussed at a daily trauma meeting. I had refused to apply a cast and suggested that this patient was in urgent need of expert orthopaedic surgical intervention.
The degree of soft tissue oedema visible is strongly suggestive that no cast was required at this stage in treatment. This injury was a highly unstable ankle joint fracture. The outline of an adequate splint, in the form of a Below Knee plaster of Paris posterior slab, is visible on the radiograph image. Ankle joint disruption of this magnitude could not be adequately supported by any cast or splint. The oedema would prevent any adequate reduction of the injury and would only serve to turn the application of a cast into a futile procedure.
The classification of this injury, as it was presented in this single view of an anterior-posterior view radiograph, is a Danis-Weber type B fibular fracture with (significant) talar shift.
The AO description for this ankle joint injury is a “Transsyndesmotic fibular fracture, with medial lesion and fracture of the posterolateral rim (Volkmann)” The AO classification is 44-B3. Follow the link to learn more about the AO system of fracture classification for long bones.
The Lauge-Hansen ankle fracture classification system uses two word descriptors
The first word describes the foot position when the injury occurred and the second illustrates the deforming force direction.
without medial malleolar fracture
with medial malleolar fracture (Danis-Weber A)
(this is the most common form of injury with a frequency of 40-70% of all injuries)
stage 1: the anteroinferior tibiofibular ligament is torn or avulsed
stage 2: talus displaces and fractures the fibula in an oblique or spiral fracture, starting at the joint (Danis-Weber B)
stage 3: tear of the posteroinferior tibiofibular ligament or fracture posterior malleolus
stage 4: tear of the deltoid ligament or transverse fracture medial malleolus
stage 1: deltoid ligament disruption or transverse medial malleolus fracture
stage 2: posterior malleolus fracture
stage 3: oblique fibular fracture (Danis-Weber C)
stage 1: deltoid ligament rupture, possibly occult or as medial mortise widening, or fracture of the medial malleolus
stage 2: involved AITFL and extension into the interosseous membrane with widening of distal tibiofibular distance
stage 3: a spiral or oblique fibular fracture (>6 cm) at the level above the talotibial joint (Danis-Weber C)
stage 4: involvement of the PITFL, or posterior malleolus fracture
The radiograph below depicts an injury classified as a Lauge-Hansen: supination-external rotation injury - stage 3
The Lauge-Hansen ankle fracture classification requires an understanding of the terminology used.
Inversion & Eversion are coronal plane movements of the ankle. Inversion & eversion are components of Supination and Pronation. Supination and pronation are triplanar movements of the foot and ankle complex.
Inversion occurs at the Hindfoot (heel). The hindfoot faces inwards and injury is likely if this movement is excessive and an inversion sprain or injury likely to occur. Eversion also occurs at the hindfoot. The hindfoot faces outwards and an injury may occur with excessive movements and stresses in this direction.
Supination comprises inversion of the hindfoot, Adduction of the forefoot, and Plantarflexion of the Talocrural area. Remember that adduction is movement towards the midline and plantarflexion is movement of the Forefoot and ankle joint towards the ground.
Talocrural is one term which refers to the ankle joint formed by the proximal talus and the distal ends of the tibia and fibula. The joint created is a synovial hinge joint. Forefoot is the term used to denote the phalanges and the metatarsals along with the associated soft tissue structures.
Pronation comprises eversion of the hindfoot, Abduction of the forefoot, and Dorsiflexion of the talocrural area. Remember that abduction is movement away from the midline and dorsiflexion is movement of the forefoot and ankle joint towards the knee.
Pronation and supination are vital movements for correct foot and ankle function. These movements must occur at appropriate times and with the necessary angular limitations which will enable the correct movement. Force absorption is facilitated by pronation and force production is facilitated by supination.
In this patient’s case, I had no choice but to refuse to apply a full cast to this particular injury. My reasoning was that urgent expert surgical intervention was essential to obtaining anything which resembled good functional alignment and subsequent function. Soft tissue oedema militated against fitting any circumferential cast accurately. The degree of joint disruption was not amenable to a simple closed reduction technique with a full cast. The application of a full circumferential cast just two days after such a significant injury could potentially imperil the patient’s healthy neurovascular status. The cast would be ill-fitting within 24 hours of application because of the amount of oedema present.